✨ Support Multiple Special Items

[yujune]

✨ What's the context?

Current AssetPickerConfig only accept single specialItemPosition and specialItemBuilder which is is not suitable for cases where multiple special items is required.

🛠 Changes being made

• Added specialItems in AssetPickerConfig and which accept list of specialItemPosition and specialItemBuilder.
• Added isPermissionLimited param to SpecialItemBuilder typedef for case where special item is required to remove when isPermissionLimited is false. Example as below.

SpecialItem(
                itemPosition: SpecialItemPosition.append,
                itemBuilder: (
                  BuildContext context,
                  AssetPathEntity? path,
                  int length,
                  bool isPermissionLimited,
                ) {
                  if (!isPermissionLimited) {
                    return null;
                  }
                  return const Center(
                    child: Text('Append Widget', textAlign: TextAlign.center),
                  );
                },
              ),

• Removed unused SpecialPosition.none enum.

✨ Result

[AlexV525]

I like this idea, would be better if we go further to support dynamic grid positions. 😆

[AlexV525]

The semantics of this field is broken since it no longer respects the builder.

[yujune]

any suggestion for this?

[AlexV525]

Maybe we can get rid of it.

[yujune]

If shouldBuildSpecialItem is removed, then it will always show loading indicator even there are special item to be displayed. Below is the current code which depends on shouldBuildSpecialItem.

 final bool shouldDisplayAssets =
              p.hasAssetsToDisplay || shouldBuildSpecialItem;
          return AnimatedSwitcher(
            duration: switchingPathDuration,
            child: shouldDisplayAssets
                ? Stack(
                    children: <Widget>[
                      RepaintBoundary(
                        child: Column(
                          children: <Widget>[
                            Expanded(child: assetsGridBuilder(context)),
                            bottomActionBar(context),
                          ],
                        ),
                      ),
                      pathEntityListBackdrop(context),
                      pathEntityListWidget(context),
                    ],
                  )
                : loadingIndicator(context),

[yujune]

shouldBuildSpecialItem has been removed, this is because assetsGridBuilder has handled the total asset count checking to display either loadingIndicator or list. Below is the code in assetsGridBuilder.

 final List<SpecialItemModel> specialItemModels = specialItems
            .map((item) {
              final specialItem = item.builder?.call(
                context,
                wrapper?.path,
                totalCount,
                permissionNotifier.value,
              );
              if (specialItem != null) {
                return SpecialItemModel(
                  position: item.position,
                  item: specialItem,
                );
              }
              return null;
            })
            .whereType<SpecialItemModel>()
            .toList();

        totalCount += specialItemModels.length;

        if (totalCount == 0 && specialItemModels.isEmpty) {
          return loadingIndicator(context);
        }

[AlexV525]

Maybe we can get rid of it.

[AlexV525]

I think we are in a relatively good state. Thanks for all your contributions! However, I'm planning some API-breaking changes such as #639, that will be pushed into the next major release, so I want to hold them together.